Improvement in adjustable desks



E. DU MMER.

mprovement in Adjustable-Desks.

Patent'd Nov. 19,1872.

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UNITED STATES PATENT OFFICE.

EDWARD DUMMER, OF NEWBURYPORT, MASSACHUSETTS.

IMPROVEMENT IN ADJUSTABLE DESKS.

Specification forming part of Letters Patent No. 133,087, dated November19, 1872.

Nature and Objects of the Invention.

My invention relates to the combination of a level plane or shelf withthe inclinable plane or table of an adjustable desk; the object of myinvention being to cause, by a simple selfadjustment, said shelf toretain its level or horizontal position Whatever may be the inclinationof the said table.

Description of the Accompanying Drawing.

Figure 1 is a side elevation of so much of an adjustable desk asembodies my invention. Fig. 2 is simply a parallelogram, illustratingthe principle on which my invention is based.

General Description.

other method of fastening may be used. E is the plane or shelf, which isto be kept in a horizontal position. F is a projection, connected firmlywith a part of the support 0. G is a rod connecting the level shelf Ewith the support 0, being hinged at H and F. I

is the hinge or one of the hinges by which the shelf is pivoted to thetable.

In the perfect working the whole is so arranged that the distance fromcenter of motion at B to that at l is the same as from the center ofmotion at F to that at H; also, the

distance from center B to center F is the same as from I to H; or, inother words, the four centers at B, I, F, and H, as it were, form thefour corners of a parallelogram, as shown in Fig. 2. With sucharrangement, whatever be the position of the inclinable table A, theshelf E will always retain a horizontal position, as shown by the dottedlines in two positions of said table, the one being nearly upright theother horizontal. Moreover, the center of motion at B is placed near thecenter of the length of the table A-that is, at a distance from thelower or front edgeof the table, so that the table is balanced as to thewhole or a part of its length.

I claim- 1. The combination, in an adjustable desk, of the shelf E,table A, support 0, plates B B pressed together by any suitable device,and the rod G connected to one of the plates B at F and to the shelf Eat H, all constructed substantially as described.

2. In an adjustable desk the table A, pivoted and supported near themiddle of its length, in combination with the shelf E, when connectedtogether, so as to operate substantially as described.

EDWARD DUMMER.

Witnesses:

F. CURTIS, LEONARD N. KENT.

